1. Technical Field
The present disclosure relates to a power management circuit and a method thereof, in particular, to a power management circuit and a method thereof for a portable electronic device having at least a USB charging port.
2. Description of Related Art
As technology advanced, portable electronic electronics such as smart phone, tablet, laptop, digital camera, video camcorder and MP3 player have been widely used in our daily life. Portable electronic devices are often equipped with rechargeable batteries supplying the required power for the carrying convenience of users. Currently as more and more power consumed functionalities including Bluetooth, WiFi and 3 G communication have been incorporated in the portable electronic devices thereby increasing the overall processing loads and the operational power consumption of the rechargeable battery thereof. Accordingly, fast charging has become a desirable objective to achieve for users of the portable electronic devices.
Currently, industries promote the use of the universal serial bus (USB) as an interface for powering the portable electronic device or for charging the rechargeable battery thereof. So that using the USB to charge the rechargeable battery of the portable electronic device has gradually become the industrial charging standard. It is known that the supply voltage of the conventional USB is 5V with maximum supply current of 500 mA. Recently, in responsive to the demands of fast charging, the USB Implementers' Forum (USB-IF) has defined new USB charging standard, i.e., the USB battery charging specification revision 1.1 (BC1.1).
Under the USB-IF BC1.1, the Available Current Allowance for each type of USB adapter have been specified. Specifically, the USB ports have been classified into three types including the Standard Downstream Port (SDP), the Charging Downstream Port (CDP), and the Dedicated Charging Port (DCP) for various electric products. Each type of USB port can support different charging current required and complex USB charger protocols. The SDP port is the current standard USB port which can only supply 500 mA maximum to charge the rechargeable battery. Whereas both the CDP port and DCP port can further increase the supply current up to 1500 mA or even to 2000 mA to accommodate type and capacity of the rechargeable battery and power consumption required for various portable electronic devices thereby reduce the charging period.
Since the USB port are classified into the SDP port, the DCP port, and the CDP port according to the newly defined USB charging specification. A USB charging port adopted has to match the charging standard in corresponding to the power consumption requirement and rechargeable battery capacity of the portable electronic device. However, the current existing portable electronic device may not have the mechanism for identifying the USB port or for operating in responsive to different type of the USB ports. Accordingly, when a user uses the wrong type of the charging port to supply the operation power or to charge the rechargeable battery, not only the charging efficiency may be lowered, but also could cause the instability of the system. In particular, when the portable electronic device has booting the system using the power received from improper USB port, the system could face overloading issue resulting from insufficient supply power and constantly switching on and off eventually leading to malfunction of the system. For instance, when the portable electronic device requires 7.5 W to turn on but was connected to a SDP port which can only supply 2.5 W to the portable electronic device. Consequently, the portable electronic device may thus experience instantly turning on and off due to insufficient power and eventually lead to the malfunction of the portable electronic device.